Chemical apparatus



July 26, 1960 R. ANNIS CHEMICAL APPARATUS Filed Dec. 22, 1955 INVENTOR ROGER L. ANNIS ATTORNEY surrounding the conduit.

United States Patent CHEMICAL APPARATUS Roger L. Annis, Painesville, Ohio, assignmto Diamond Alkali Company, Cleveland, Ohio, a corporation of Delaware Filed Dec. 22, 1955, Ser. No. 554,789

2 Claims. (Cl. 257-86 This invention relates to a heat exchange device, and more particularly relates to a heat exchange jacket surrounding a conduit in which the temperature of a material being transported may be controlled, and still more particularly relates to a heat exchange jacket surrounding the flight of a screw conveyer in which the temperature of a material being transported therein is to be maintained within desired limits. The invention is especially useful in heat exchange jackets for screw conveyers for continuously feeding granular reactants to a reaction zone maintained at a temperature higher than that at which the feed material undergoes a change of state.

It has heretofore been proposed to provide a heat exchange jacket surrounding a conduit in which the temperature of material being transported in the conduit'is to be controlled. Such heat exchange jackets are illustrated by the shell of a sheet and tube heat exchanger in which the shell surrounds a tube bundle which is attached to two tube sheets at the ends of the tube bundle. The heat exchange medium is circulated either within the tube bundle or within the jacket surrounding the tube bundle, the material to be heated or cooled being circulated in the other of the two in indirect heat exchange relationship with the heat transfer medium. In such a heat exchanger the heat exchange material may be introduced at one end of the device and removed from. the other end, the flow of heat exchange material being countercurrent to the flow of material, the temperature of which is to be raised or lowered. Alternatively, the jacket may be divided into two compartments which intercornmunicate near one end of the jacket with provision for introduction of heat exchange material into one of the compartments and withdrawal from the second compartment, at the other end of the jacket.

Similarly, it has heretofore been proposed to provide a heat, exchange jacket for a screw conveyer, the heat exchange jacket being so arranged that heat exchange fluid is introduced either concurrently or countercurrent- 1y to the direction of flow of the material being trans ported in the screw conveyer.

It has now been found that a much more uniform temperatureof the material being transported in a conduit having a heat exchange jacket may be obtained through the use of simultaneous countercurrent and concurrent flow of heat exchange material within the jacket The simultaneous concurrent and countercurrent flow of heat exchange material contemplated, in accordance with the present invention, involves, in effect, maintaining two streams of heat ex changematerial, each in heatexchange relationship with the other, as well as with material being transported within the conduit to which the device of the present in vention attaches. This is accomplished by reversing the direction of flow of the stream of heat exchange material at the endof the heat exchanger opposite that at which it is introduced, and withdrawing such material at the same end of the heat exchanger at which it was intro duced.

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The specific instrumentalities involved include meanspositioned Within an annular chamber between inner and outer tubular conduits, which divide the chamber formed by the two conduits into adjacent convolute or helical compartments .intercommunicating at one end of the chamber, entrance means for circulation of heat exchange material provided to one of the compartments, and egress means provided for removing heat exchange material from the other of the compartments, said entrance and egress means being positioned opposite the end of the chamber at which the compartments intercommunicate.

' Thus, the present invention .is directed to a heat ex change jacket which maybe used to transfer heat to a cold material being transported in the inner conduit, by

means of a heated fluid circulating within the helical compartments 'of the jacket, or may be used to cool a heated material being transported in the inner chamber, by means of a cold fluid circulated in the helicalcompartments, and is especially effective in providing heat exchangebetween heat exchange fluid circulated within the helical compartments and the innermost conduit to minimize temperature differences existing in the innermost conduit as material therein moves from one end to the,

other. Moreover, the design of the helical compartments within the annularchamber permits the entrance and egress means for the compartments to be at the same end of the heat exchange device,,decreases terminal temperature ditferences in respect to both the heat exchange fluid circulating within the compartments and the material being transferred in the innermost conduit, and at the same time increases the heat exchange rate within the device by creating increased turbulence of the heat transfer fluid .in the .helical compartments as well as by i ncreasing the total available heat'exchange surface.

Accordingly, the present invention is directed to a heat exchange device comprising the combination of an inner tubular member, an outer tubular member spaced apart from said inner tubular member, means attached region of said opposite end of said chamber to said egress means.

The invention may be more fully described in connection with the drawings attached hereto and made a part hereof, wherein;

Fig. l is a vertical section of a heat exchange device employing the principles of the present invention in a single open end screw flight; and

Fig, 2.is a side elevation of the heat exchange device of Fig. 1 with parts broken away showing internal structure and relationship of the parts of the apparatus.

.In the drawings, 2 is the outermost shell of a jacket surrounding a conduit 4 in which material to be transferred may be subjected to temperature changes during its passage through the conduit. The chamber 6, formed by spaced-apart conduits 2 and 4, is annular, each of tubular members Sand 10 representing entrance or egress means for the chamber 6.

The chamber 6 is divided into adjacent compartments, by means 12 and 1211, which, in the drawings, are bars helically wrapped around conduit 4, and which divide the chamber 6 into two adjacent helical compartments. Bars 12 and 12a are preferably attached to both 0uter- 0 conduit 2' and inner conduit 4 in such a manner as to prevent substantial leakage of heat exchange material from one compartment to the other, a small amount of leakage not defeating the practical application, and extend to less than the full length of the chamber 6, whereby the adjacent compartments intercommunicate at annulus means 14 formed by outer conduit 2, inner conduit 4, and closure means 16.

As shown in the drawings, the inner conduit 4 may house a screw flight 18 which receives material to be transported within the conduit through feed means 20. Driving means for the screw are provided by pulley 22, which is driven by a suitable source of power not shown and may be provided with heating means 24 and 26 for cantilever support of the screw flight upon supporting members 28, 30, 32, and base 34.

In operating the device shown on the drawings, heat exchange material is introduced into the annular chamber formed between the inner conduit 4 and the outer conduit 2, through either of the tubular members 8 or 10, the heat exchange material passing through one of the compartments formed within the chamber 6, toward the end of the conduit opposite that at which the heat exchange fluid is introduced, until it reaches the annulus 14 by means of which the compartments intercommunicate. The heat exchange material is then transferred to the other of the compartments within the chamber 6 and passes toward the opposite end to the other of the means 8 or 10, depending upon which of the two tubular members was used for introduction of the heat exchange material. Material to be transferred by the screw flight is then introduced into feed means 20, and power is applied to pulley 22 to cause rotation of screw 18, and move the material from feed means 20 through conduit 4.

In this manner, material passing through conduit 4 is subjected to heat transfer with a heat transfer material which in one-half of its passage through the jacketis moving countercurrently to the material in the conduit, and in the other half of its passage is moving concurrently thereto. Moreover, the flow of heat exchange material in each of the two compartments is countercurrent with respect to the other as shown in Fig. 2,, wherein it is evident that material introduced into the heat exchange jacket through tubular member 10, passes in a helical path toward the opposite end of the jacket as indicated by the arrows showing a generally clockwise direction along the helix, toward the annulus 14. The heat exchange material is subjected to a high degree of turbulence in the region of the annulus 14, and finally is reversed to a counterclockwise direction, as indicated by the arrows in moving along the helical compartment leading to tubular member 8 which serves as egress means for the heat exchanger.

The heat exchanger of the present invention is especially useful where a reactant, or mixture of reactants, is to be fed to a high temperature reaction zone, and the reactant, or mixture of reactants, must be maintained at a temperature such that a change in state does not take place prior to discharge into the reaction zone. Thus, for example, in the manufacture of alkali metal silicates from an alkali metal carbonate or alkali metal hydroxide, and sand, the mixture of reactants is conducted to a furnace wherein the temperature may range from about 1600 F. to as high as 2500 F. In such an operation where it is economically. desirable to feed reactants to the furnace continuously, the discharge end of the screw conveyer would be subjected to temperatures considerably above that of the melting point of the alkali material and above that at which a screw conveyer could operate without damage to both the screw and housing. It would, therefore, be essential to maintain the reactants in the granular free flowing state until such a time as they reach the reaction zone, and to protect the screw and housing, especially that portion which projects into the furnace, from undue strain due to the intense heat encountered therein. The annulus 14 at the end of the screw conveyer conduit, at which the compartments intercommunicate in providing means for effecting a high degree of turbulence of heat exchange material, assures such protection to the metal parts of the apparatus, while at the same time the adjacent helical compartments within the chamber 6 assure heat exchange between the incoming heat exchange material and that passing toward egress means from the chamber 6. By this means large differences in temperatures of the heat exchange material between any two or more points within the system are prevented, and the temperature of material transported within the conduit by the screw is easily controlled within ranges which preclude a change of state due to temperature.

While there have been described various embodiments of the invention, the apparatus described is not intended to be understood as limiting the scope of the invention as it is realized that changes therewithin are possible and it is further intended that each element recited in any of the following claims is to be understood as referring to all equivalent elements for accomplishing substantially the same results in substantially the same or equivalent manner, it being intended to cover the invention broadly in whatever form its principle may be utilized.

What is claimed is:

1. In combination with a furnace, a screw conveyor adapted for use in said furnace having a screw flight located within a tubular conduit, feed means and drive means located at one end of said conveyor outside of the furnace with the main portion of the conveyor extending into said furnace, an outer shell surrounding said tubular conduit and cooperating therewith to provide an annular heat exchange chamber therebetween having closure members at opposite ends and containing helically wrapped bars separating the chamber into separate compartments which intercommunicate in an annulus section at the end opposite the feed means, said heat exchange chamber extending a substantial distance into the furnace beyond the end of the screw flight and having ingress and egress means outside of said furnace at the end opposite the annulus section.

2. A screw conveyor adapted for use in a furnace having feed means and drive means located outside of the furnace and having a screw flight extending into the furnace, a tubular conduit surrounding the screw flight and an outer shell surrounding the tubular conduit with closure means at opposite ends providing therebetweeu a heat exchange chamber, the heat exchange chamber containing helically wrapped bars separating the chamber into separate compartments, an annulus section at the end opposite the feed means providing intercommunication between the separate heat exchange compartments and ingress and egress means located at the end of the chamber outside of the furnace, said heat exchange chamber surrounding the entire portion of the screw flight within the furnace and extending a substantial distance into the furnace beyond the end of the screw flight, the feed means, drive means, and ingress and egress to the heat exchange chamber located outside of the furnace and the balance of the screw conveyor located within the furnace.

References Cited in the file of this patent- UNITED STATES PATENTS 916,437 Griffen et al. Mar. 30, 1909 1,598,721 Hitchcock Sept. 7, 1926 1,816,307 Von Reis July 28, 1931 1,831,912 Hoffman Nov. 17, 1931 1,993,264 Duttweiler Mar. 5, 1935 FOREIGN PATENTS 688,361 Great Britain Mar. 4, 1953 

